This invention relates to an apparatus for making bags or sacks from a preferably gusseted continuous tubular film of thermoplastic material. The apparatus is of a type which comprises guide rollers and pinch rollers by which the leading end of a freely vertically depending continuous tubular film is adapted to be advanced in steps each corresponding to the length of one bag or sack to a position between welding jaws of a welding device, which are adapted to perform opening and closing movements in a horizontal plane to form successive weld seams in the film. The apparatus, also has a transverse cutter, which is disposed below the welding jaws, and pairs of grippers, which are disposed below the cutter. The grippers are provided on a conveyor by which the bags or sacks which have been successively severed from the film are adapted to be moved through a cooling section for cooling the bottom weld seam of each bag or sack to a transfer apparatus for conveying the bags or sacks to a filling device.
When materials are to be filled into sacks by manufacturers and/or fillers, this is often performed by means of filling machines, which are preceded by a machine for making the sacks to be filled. In the latter machine a preferably gusseted continuous tubular film of thermoplastic plastics is intermittently withdrawn from a supply roll and sacks consisting of tubular film sections provided with bottom welds are severed from the continuous tubular film shortly before the sacks are filled. When the sacks have been filled, they are provided with a closing seam at their top end. To ensure an adequate cooling of the bottom seam weld which has been made shortly before the sacks are filled so that said seam will have an adequate strength before the sacks are filled, it is advisable to feed the sacks provided to the filling apparatus through a cooling section.
German Patent Specification 24 18 228 describes an apparatus of the kind described hereinbefore and in which the cooling section has two mutually opposed chain conveyors, which are synchronously driven and have endless chains which are trained each around two chain sprockets on vertical axes. The chains carry spaced apart grippers, which while moving along the confronting and coplanar inner courses of the chains grip mutually opposite edge portions of the bags which have been provided with bottom welds and convey the bags to a transfer apparatus for conveying the sacks to the filling device. The known apparatus is rather expensive because two revolving endless chains and means for driving them are required. Only the grippers moving along the two confronting inner courses of the chains are utilized to convey the sacks whereas the grippers have no conveying function as they move around the driving and reversing sprockets and along the outer chain courses.
British Patent Specification 919,392 discloses an apparatus which is used to make and fill sacks and comprises a turret that is rotated in angular steps. In this apparatus the bottom seam is welded after the continuous tubular film has been advanced to the extent of one sack length so that the time required for a step is determined by the time required for the welding operation and by the time which is required to advance the continuous tubular film to the extent of one sack length. Also, this apparatus cannot be adjusted in a simple manner to accommodate different sack sizes because the welding device for forming the bottom seam is spaced a constant distance below the grippers whereby the elevation of the welding jaws must be changed for a change of the length of the sack.
Moreover, one of the stations associated with the turret constitutes the filling station so that a sufficiently long time for cooling the bottom seam weld is not assured.
A similar turret-like apparatus for making and filling sacks or bag is known from German Patent Specification 26 08 456.